Examples similar to the examples from the ANTLR tutorial in the PCCTS reference guide:

* Evaluating polynomials - poly.rb
  Similar to the polynomials example on page 41. Differences:
    Only takes one assignment/polynomial at a time
    No need to specify 
  
* Symbolic differentiation - differentiate.rb
  Similar to the example on page 68. Differences:
    Multiple variables ok in expression
    The variable to differentiate wrt can be specified

